1. Field of the Invention
The present invention relates to pacer housings and more particularly to those parts of the housing intended for connection to the electrode leads.
2. Description of the Prior Art
Implantable pacers normally have a pacer housing (also called can) containing electronic circuitry and a unit for electric power as well as different electrodes which are connected to the interior parts in the pacer housing and which are to be implanted in or in the vicinity of the heart. The electrodes are connected to the pacer by means of leads. The internal parts of the pacers have to be well protected against the internal environment, especially the body fluids in the body for a long period of time, which places strict requirements on all entries into the interior of the can and especially on the connections of the leads to the housing. At the same time it should be possible to disconnect the pacer from the implanted leads for replacement or servicing of the pacer. The connective parts of the pacer and the leads have largely been standardized so as to encompass a relatively deep female socket having a number of contact surfaces whereas the leads are provided with a male part comprising one or several corresponding peripheral, generally circular contact surfaces.
At present the connective part of the pacer housing containing the female socket is made of a transparent material, normally of epoxy resin, which is molded onto the housing and onto contacts extending outwardly from the housing. The male part of the leads is normally locked by means of set screws, although other fastening means have been suggested. The positioning and alignment of the different contact surfaces and of the fastening means or metallic threads for the set screws prior to the molding of the connective part is, however, complicated and the delay in the manufacturing process incurred by the curing of the epoxy resin is considerable.
It would thus be desirable if the molding procedure could be dispensed with.
It has been discussed that these complexities could be avoided by designing the pacer with a socket located inside the metal housing. This kind of sockets, sometimes termed “black holes”, are not used at present.
U.S. Pat. No. 4,934,366 and U.S. Pat. No. 5,324,311, both of which are incorporated by reference, describe two interior sockets or black holes for pacers. Both designs employ a tubular member formed by a number of longitudinally alternating sections respectively made of metal and insulating ceramics. An end section of metal can be welded or bonded to an opening in the pacer housing by means of a flange. The use of different materials, however, sets high standards in regard to precision and durability of the components as well as in the assembly procedure thereof. This is especially important since the interior sockets must meet very high standards regarding the integrity of the interior of the pacer housing during long times of implantation in a demanding environment. The manufacture of these known sockets thus is relatively complicated.